The present invention relates to a fuel cell power plant and more particularly to a control system for a fan in the coolant system of the fuel cell power plant.
Fuel cell power plants have been proposed for use in vehicular applications to replace internal combustion engines, as well as in portable and stationary distributed electrical power generation applications. In such applications, the fuel cell power plant is a complex arrangement of systems which include a fuel processing system for locally generating hydrogen from a hydrocarbon fuel such as gasoline, a fuel cell stack for converting hydrogen and air to electrical energy and water, and a power train for converting electrical energy to mechanical energy. The various components of these systems generate heat which must be dissipated to maintain efficient, prolonged operation of the components of the fuel cell power plant.
A liquid to air coolant system is typically employed to extract heat from the fuel cell power plant and to dissipate the extracted heat into the environment. Such coolant systems employ a coolant loop which garners heat from various components in the fuel cell power plant. The coolant loop includes a heat exchanger such as a radiator to transfer heat from the heated coolant to air flowing through the heat exchanger. Often times a cooling fan is employed to facilitate the air flow through the heat exchanger. In this way the coolant system functions in a similar manner to the coolant system of a conventional vehicle having an internal combustion engine.
Control of the cooling fan in such conventional systems have been based on the temperature of the coolant at a given point in the coolant loop. Specifically, the cooling fan is disabled when the temperature of the coolant is below a threshold value and enabled when the temperature of the coolant is above the threshold value. While such controls may work adequately for certain operating states of a fuel cell power plant, it is not readily adaptable to the wide range of operating states that may be required, particularly where the fuel cell power plant has a relatively large turndown ratio to respond to transient load demands such as in a vehicular application.
Some applications may also employ multiple coolant loops for separate cooling of components having different thermal operating ranges. Such systems typically employ multiple radiators or radiator sections each having a dedicate fan assembly. Each coolant loop is operated independently of the other coolant loops resulting in additional mass and added complexity to the control of such cooling systems. Accordingly, there is a need to provide an efficient and simple coolant fan control system for fuel cell systems.
A control system and method according to the present invention controls the operation of the cooling fan in a coolant system having a first coolant loop and a second coolant loop. A fan controller generates a fan control signal based on a first input signal from the first coolant loop and a second input signal from the second coolant loop. The first input signal is a function of the waste heat energy in the first coolant loop, and the second input signal is a function of the temperature in the second coolant loop. The fan control signal may also be generated based on a third input signal which is a function of a localized ambient temperature such as the under hood temperature of a vehicle. The present invention enables operation of a single coolant fan assembly based on a plurality of independent input signals associated with various coolant subsystems in the fuel cell power plant.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the present invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.